Congestion may occur in a communication network when a network element such as a switch or a router is required to deliver traffic to the communication network beyond the link capabilities. Some congestion mitigation methods are based on notifying a traffic source to reduce its transmission rate when or even before congestion occurs.
Methods for congestion mitigation are known in the art. For example, U.S. Pat. No. 6,556,578 describes a method for managing a buffer pool containing a plurality of queues based on consideration of both (a) when to drop a packet and (b) from which queue the packet should be dropped. According to the method a packet drop is signaled with the global average queue occupancy exceeds a maximum threshold and is signaled on a probabilistic basis when the global occupancy is between a minimum threshold and the maximum threshold. Each queue has a particular local threshold value associated with it and is considered to be “offending” when its buffer occupancy exceeds its local threshold. When a packet drop is signaled, one of the offending queues is selected using a hierarchical, unweighted round robin selection scheme which ensures that offending queues are selected in a fair manner. A packet is then dropped from the selected offending queue.
U.S. Patent Application Publication 2014/0328175 describes a method that includes estimating a current queuing latency, the estimated current queuing latency being associated with a queue of packets maintained in a buffer. The method also includes calculating a current drop or mark probability, the current drop or mark probability being associated with a probability that packets associated with the queue of packets will be dropped or marked. A rate at which the packets associated with the queue of packets are de-queued from the buffer is estimated in order to estimate the current queuing latency. The current drop or mark probability is calculated using the current estimated queuing latency.